The present invention relates to a detergent composition which is thickened without using a thickener, has excellent temperature stability and can impart the skin with good touch feeling after washing.
It is the common practice to gel a detergent composition for the skin or hair by using a thickener in order to prevent it from easily flowing away from the body upon use. Incorporation of a thickener in a detergent composition is however accompanied with the problem that stirring under heat is necessary and thus, the treatment of it is very cumbersome. Moreover, a gel thus obtained involves a problem in stability, because it is easily influenced by a temperature or pH.
With a view to overcoming these problems, a viscous composition (Japanese Patent Application Laid-Open No. SHO 58-79099) which is gelled by the addition of amidobetaine and salts without using an ordinary thickener is proposed. Such a composition, when used as a detergent composition, cannot impart the skin with moisturized feeling after washing and good skin touch is not available.
An object of the present invention is therefore to provide a detergent composition which can be thickened easily without using a thickener, has excellent temperature stability and can impart the skin with good touch feeling after washing.
The present inventors combined an amphoteric surfactant and a compound containing, in the molecule thereof, a carboxyl group and an amino group or a quaternary ammonium group at a specific ratio. It has been found that based on this combination, a detergent composition which is thickened easily by mixing these components at room temperature without using a thickener, has excellent temperature stability and after washing with it, can impart the skin with good touch feeling such as moisturized feeling is available. Thus, the present inventors completed the present invention.
In the present invention, there is thus provided a detergent composition comprising the following components (a) and (b):
As the amphoteric surfactant (a) to be used in the present invention, carboxybetaine amphoteric surfactants are preferred. Specific examples include alkylamidobetaines (alkyl-CONH(CH2)nxe2x80x94N+(CH3)2xe2x80x94CH2COOxe2x80x94), alkylaminobetaines (alkyl-NH(CH2)nxe2x80x94N+(CH3)2xe2x80x94CH2COOxe2x80x94), alkylbetaines (alkyl-N+(CH3)2xe2x80x94CH2COOxe2x80x94), and 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazoliniumbetaines. Among them, those having a C8-20 alkyl group or acyl group are particularly preferred.
As the component (a), one or more amphoteric surfactants can be used in combination. The component (a) is incorporated in a total amount of 2 to 35 wt. % (which will hereinafter be called %, simply), preferably 2 to 20% based on the whole composition. Amounts less than 2% cannot thicken the system sufficiently, while those exceeding 35% may solidify the system and damage the appearance.
The compound (b) used in the present invention is other than the component (a) and contains, in its molecule, a carboxyl group and an amino group or a quaternary ammonium group. As such compounds, neutral amino acids, betaine compounds and ethylenediaminetetraacetate salts are preferred. Specific examples of the neutral amino acid include glycine, sarcosine, L-serine, xcex2-alanine and aminobutyric acid. Specific examples of the betaine compounds include those having 1 to 5 carbon atoms in each of the alkyl chains, for example, trimethylglycine, trimethylserine, hydroxyethyldimethylglycine and monoethanolcarboxybetaine (HOCH2CH2N+xe2x80x94(CH3)2xe2x80x94CH2CH2CH2COOxe2x80x94).
Among them, betaine compounds having 1 to 5 carbon atoms in each of the alkyl chains are preferred, with trimethylglycine being more preferred, because it brings about sufficient thickening effects and moisture retention effects.
As the component (b), one or more of the above-described compounds can be used in combination. The component (b) is added in an amount of 6 to 40%, preferably 6 to 30%, particularly preferably 6 to 20% based on the whole composition. Amounts less than 6% cannot thicken the system sufficiently, while those exceeding 40% happen to solidify the system. For the use as a detergent, amounts up to 40% are preferred.
It is preferred that the weight ratio of the component (a) to the component (b) ((a)/(b)) falls within a range of 1/10 to 10/1, particularly from 1/5 to 5/1 and more preferably from 1/5 to 3/1. At a weight ratio within the above-described range, thickening occurs easily and a gel composition is available.
To the detergent composition of the present invention, a surfactant other than the above-described one can also be added. Examples include anionic surfactants such as alkyl sulfate salts, alkyl sulfonate salts, alkyl phosphate salts, polyoxyethylene alkyl sulfate salts, alkylbenzene sulfonate salts, N-acylsarcosine salts, N-acyl-N-methyltaurine salts, alfaolefin sulfonate salts, higher fatty acid ester sulfonate salts, alkyl ether acetate salts, polyoxyethylene alkyl ether acetate salts and fatty acid soap; and nonionic surfactants such as fatty acid amides, polyoxyethylene alkyl ethers, saccharide esters, saccharide ethers and saccharide amides.
In addition, humectants such as propylene glycol, sorbitol and glycerin, pearling agents, perfumes, colorants, ultraviolet absorbers, antioxidants, bactericides, anti-inflammatory agents and antiseptics can be added as another additive.
The detergent composition of the present invention can be obtained as a transparent gel composition by mixing the components (a) and (b), optional components and water at room temperature, thereby easily thickening. It can also be prepared as an opaque composition by adding a turbidity imparting agent. Water is added in an amount of 40 to 70% based on the whole composition, with 50 to 70% being particularly preferred. By adjusting the amount of each of the components, the desired viscosity is available. For example, viscosity at 25xc2x0 C. is preferably adjusted to 1,000 to 1,000,000 mPa""s, with 10,000 to 100,000 mPa""s being particularly preferred.
The detergent composition of the present invention thus available is used for washing of the skin, hair or the like and it is particularly suited for use as a skin detergent, more preferably face wash.